In 2012, whispers began emerging about some mythical footage of Frank Zappa jamming with Pink Floyd in 1969. There is photo proof of the performance that has been circulating for decades, and a sketchy bootleg recording that has been pulled from YouTube whenever it poked its head up.

However, actual video footage has been elusive. That was until the release of the mammoth Pink Floyd boxset that came out last year.

Watch rare footage of Frank Zappa jamming through Interstellar Overdrive with Pink Floyd in at a festival in Belgium in 1969.

The video in question sees Zappa on lead guitar for 20 minute rendition of Interstellar Overdrive, one of Syd Barrett’s most memorable contributions to the Pink Floyd catalogue.

The gig took place on October 25, 1969 at Festival Actuel in Amougies, Belgium. Speaking about the experience years later, Floyd drummer Nick Mason lays praise on Zappa:

“Frank Zappa is really one of those rare musicians that can play with us. The little he did in Amougies was terribly correct. But he’s the exception. Our music and the way we behave on stage, makes it very hard to improvise with us.”

Zappa, on the other hand, apparently had no recollection of the performance whatsoever.

Watch a 14 minute version of the jam below. Unfortunately the final seven minutes are cut, which is a bummer ’cause supposedly they’re the best.

Here is a little more info on the gig from the notes of the 1969 The Amougies Tapes Zappa bootleg:

“Frank Zappa was present at the festival in a twofold capacity. First, as Captain Beefheart’s road manager; secondly, as M.C., assisting Pierre Lattes, a famous radio/TV presenter at the time (and the pop music editor for Actuel magazine). The latter task proved problematic given Zappa’s limited French, the prevailing language among the audience, who themselves didn’t seem to understand much English. Instead, Zappa relinquished his M.C. job for one of occasional guest guitarist. He plays with almost everybody, especially with Pink Floyd, Blossom Toes, Archie Shepp and Aynsley Dunbar, a fabulous drummer he will hire shortly thereafter. He introduces his friend Captain Beefheart and provides a powerful stimulant to all the other musicians. Most legendary, of course, is Frank Zappa’s jam with Pink Floyd on a very extended “Interstellar Overdrive”. The festival was filmed by Jerome Laperrousaz, and the film was to be called MUSIC POWER. Due to objections from various bands (most notably Pink Floyd) whose permission hadn’t been properly secured, the film was never officially released.”